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424 17 Crocodyliforms from the Late Cretaceous of Grand Staircase–Escalante National Monument and Vicinity, Southern Utah, U.S.A. Randall B. Irmis, J. Howard Hutchison, Joseph J. W. Sertich, and Alan L. Titus Although the Kaiparowits Basin of southern Utah contains an excellent Late Cretaceous stratigraphic record of nonmarine fossiliferous sediments, crocodyliforms from these deposits remain poorly known. Isolated teeth and osteoderms from the Dakota and Straight Cliffs formations document the presence of widespread large clades such as Mesoeucrocodylia and Neosuchia, but finer taxonomic resolution is not currently possible. The record from the middle Campanian Wahweap Formation is similarly fragmentary but also includes specimens assignable to Crocodylia, the crown group of crocodyliforms. By far the best-known crocodyliform assemblage from the Late Cretaceous of Utah is that of the late Campanian Kaiparowits Formation, which preserves the remains of at least three alligatoroids: Deinosuchus hatcheri, Brachychampsa, and an unnamed small alligatoroid that lacks globidont teeth. The Wahweap and Kaiparowits formations also preserve large rectangular osteoderms of an indeterminate basal neosuchian that might be related to the goniopholidid Denazinosuchus from the late Campanian of the San Juan Basin in northern New Mexico but could also pertain to a late surviving pholidosaurid. The Kaiparowits Formation crocodyliform assemblage is most similar to that of the Fruitland and Kirtland formations in the San Juan Basin, and differs from more northerly assemblages in Montana and Alberta. Kaiparowits crocodyliforms provide additional evidence for a distinct southern Laramidian vertebrate faunal province during the Campanian and possible climate-induced northern migration of southern taxa during the Maastrichtian. Introduction Crocodyliformes, a subclade of Crocodylomorpha, includes nearly all known (fossil and living) long-snouted aquatic and semiaquatic forms that are typically thought of as the prototypical crocodylian form (i.e., modern crocodylids and alligatorids). Extinct taxa also include a host of semiterrestrial and likely fully terrestrial forms that include shortskulled omnivores/herbivores (notosuchians) and tall-skulled macropredators (peirosaurids, sebecosuchians, and pristichampsids ). This clade reached its peak in both diversity and disparity during the Cretaceous and Paleogene periods (e.g., Markwick, 1998), with highly distinct Laurasian and Gondwanan assemblages (Turner, 2004). Crocodyliforms are a common component of nonmarine vertebrate assemblages from the Late Cretaceous of the Western Interior (Markwick, 1998; Eaton, Cifelli, et al. 1999; Peng, Russell, and Brinkman, 2001; Wu, 2005; Lucas et al., 2006). Crocodyliform fossils from Laramidia have become increasingly important in understanding the origin of Crocodylia (crown-group crocodyliforms), and in particular alligatoroids (Erickson, 1972; Wu, Brinkman, and Russell, 1996a; Brochu, 1997, 1999, 2003, 2004; Wu, Russell, and Brinkman, 2001). However, nearly all of these taxa come from northern Laramidia (Montana and Canada), whereas southern Late Cretaceous assemblages are poorly known. A recent review identified only three taxa from the wellstudied San Juan Basin in northern New Mexico (Lucas et al., 2006), and crocodyliforms from the Late Cretaceous of southern Utah have only been mentioned in passing or in faunal lists (Eaton, 1991; Gillette and Hayden, 1997; Eaton and Cifelli, 1998; Eaton, Cifelli, et al. 1999; Eaton, Diem, 1999; Hutchison et al., 1998; Wiersma, Hutchison, and Gates, 2004; Titus et al., 2005; Gates et al., 2010; Sampson, Loewen, et al., 2010). These southern records are critically important for understanding Late Cretaceous nonmarine vertebrate biogeography, where there is evidence for latitudinally arrayed endemic faunas that show limited mixing over time (Gates et al., 2010; Sampson, Loewen, et al., 2010; Sampson, Gates, et al., 2010; Hutchison et al., this volume, Chapter 13). Here, we review the crocodyliform fossil record of Late Cretaceous nonmarine units in southern Utah, with a focus on the Campanian Wahweap and Kaiparowits formations of the Kaiparowits Plateau. We discuss the identity of crocodyliform fossils recovered over the past 25 years of fieldwork, and discuss their implications for Late Cretaceous Western Interior biogeography. These fossils are discussed by formation in Crocodyliforms from the Late Cretaceous, Southern Utah 425 the following stratigraphic order: Dakota Formation (upper Cenomanian), Straight Cliffs Formation (Turonian through Santonian), Wahweap Formation (middle Campanian), and Kaiparowits Formation (upper Campanian). Institutional Abbreviations MNA, Museum of Northern Arizona, Flagstaff, Arizona; UCMP, University of California Museum of Paleontology, Berkeley, California; UMNH, Natural History Museum of Utah, Salt Lake City, Utah. Crocodyliform Fossil Assemblages Dakota Formation CROCODYLIFORMES Hay, 1930, sensu Benton and Clark, 1988 MESOEUCROCODYLIA Whetstone and Whybrow, 1983 Specimens MNA V10402, 10403, and V10406 (MNA Loc. 939); MNA V10407 (MNA Loc. 1008); MNA V10408 (MNA Loc. 1064), MNA V10404 and V10405 (MNA Loc. 1067); MNA V10409 (MNA Loc. 1068–3); MNA V10410 (MNA Loc. 1071–1); and...

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